Claim CA500:

Natural selection, or "survival of the fittest," is tautologous (i.e.,
uses circular reasoning) because it says that the fittest individuals
leave the most offspring, but it defines the fittest individuals as those
that leave the most offspring.

Response:

"Survival of the fittest" is a poor way to think about evolution.
Darwin himself did not use the phrase in the first edition of Origin
of Species. What Darwin said is that heritable variations lead to
differential reproductive success. This is not circular or
tautologous. It is a prediction that can be, and has been,
experimentally verified (Weiner 1994).

The phrase cannot be a tautology if it is not trivially true. Yet there
have been theories proposing that the fittest individuals perish:

Alpheus Hyatt proposed that lineages, like individuals, inevitably
go through stages of youth, maturity, old age, and death. Towards
the end of this cycle, the fittest individuals are more likely to
perish than others (Hyatt 1866; Lefalophodon n.d.).

The theory of orthogenesis says that certain trends, once started,
kept progressing even though they become detrimental and lead to
extinction. For example, it was held that Irish elks, which had
enormous antlers, died out because the size increase became too
much to support.

The "fittest" individuals could be considered those that are
ideally suited to a particular environment. Such ideal adaptation,
however, comes at the cost of being more poorly adapted to other
environments. If the environment changes, the fittest individuals
from it will no longer be well adapted to any environment, and the
less fit but more widely adapted organisms will survive.

The fittest, to Darwin, were not those which survived, but those
which could be expected to survive on the basis of their traits. For
example, wild dogs selectively prey on impalas which are weaker
according to bone marrow index (Pole et al. 2003). With that
definition, survival of the fittest is not a tautology. Similarly,
survival can be defined not in terms of the individual's life span,
but in terms of leaving a relatively large contribution to the next
generation. Defined thus, survival of the fittest becomes
more or less what Darwin said, and is not a tautology.

References:

Hyatt, Alpheus. 1866. On the paralellism between the different stages
of life in the individual and those in the entire group of the
molluscous order Tetrabranchiata. Memoirs Read Before the Boston
Society of Natural History 1: 193-209.